The present invention relates to a video inspection system and, more particularly, to a real time video inspection system having sixteen levels of grey shade resolution.
It is known to employ closed circuit television for process control. For example, U.S. Pat. No. 3,243,509 to Hans Sut discloses a system which employs a TV camera to detect the phase boundary between the solid and liquid phases of a semiconductor rod in a zone melting process. In U.S. Pat. No. 4,064,534 to Tung Chang Chen et al a TV camera is employed as part of a quality control system in the manufacture of glass bottles, the outline of the finished bottle being compared with that of a reference bottle. In U.S. Pat. No. 4,135,204 to Ray E. Davis, Jr. et al., which is assigned to the assignee of the present invention, a TV camera is used to control the growth of a thermometer end opening blister in a heated hollow glass rod by monitoring and iteratively controlling the growth of the edges of the blister using edge detection techniques.
These prior art systems are directed to situations where the parameter of interest is an edge or boundary which may be compared with a pre-existing reference. There are many applications, however, where edge or boundary detection is totally inadequate. These applications include, for example, pattern recognition and area measurement.
The present invention overcomes the limitations of the prior art systems and comprises a high speed, real time video inspection system having sixteen levels of grey shade resolution which is suitable for both pattern recognition and area measurement applications. The video inspection system of the present invention is small, powerful, fast, relatively inexpensive and very reliable.
In an illustrative embodiment the present invention is employed in a quality control application to compare labels on bottles coming off a high speed fill line with a reference label to determine whether the bottles bear the correct labels and whether the copy on the labels has been smudged or otherwise damaged. In a preferred mode of operation the difference, if any, between the reference label and the label being inspected is displayed on a TV monitor for viewing by an operator. The advantages of this application are readily apparent since now it is possible to have 100% quality control inspection without incurring large labor expenditures.
In a preferred embodiment the present invention employs a solid state TV camera utilizing, for example, a 244 by 236 array of elements, each of the 57,584 elements constituting a "pixel" or elemental part of the overall picture. The unstructured digital data from the TV camera goes to an interface which has a direct memory access (DMA) channel. The interface/DMA takes the real time video information and structures the data, using sixteen grey shade levels, and combines four "pixels" into each word. In addition to the TV camera and interface/DMA, the present invention employs a RAM memory, a processor, a computer (with an associated operator control terminal) and graphics imaging circuitry (with an associated TV monitor). The interface/DMA, RAM memory, processor, computer and graphics imaging circuitry are all interconnected by means of a "multibus" which carries data, control and address signals. The interface/DMA synchronizes the TV camera with the multibus and transfers the TV image in real time to any desired location in the RAM memory. Once the image is in the RAM memory, processing occurs on two levels. The computer provides the supervisory tasks for serial communication, memory management input/output processing, data acquisition and display whereas the processor is used for high speed array processing of the data in the RAM memory. The system software is located in the computer.
As already noted, the video inspection system of the present invention is readily adaptable to numerous applications involving pattern recognition and area measurement. Applications involving pattern recognition include the inspection of completed printed circuit boards, the detection of flaws in manufactured items, intruder detection, the analysis of fingerprints, the detection of foreign objects in containers before they are filled and as part of aircraft landing or collision avoidance systems. Applications involving area measurement include the measurement of machined parts, the measurement of heart wall thickness, the semi-automated analysis of X-rays and the precision area measurement of irregular objects. With the addition of positioning information, the video inspection system of the present invention can also be used to generate visual sensory signals for robotics.
The video inspection system of the present invention is so versatile because it can acquire and process the full range of data available from the sensor. Moreover, by using standard optical components with the TV camera the images available for analysis extend from the micro scale to the macro scale, from images of microelectronic circuitry to images of planetary bodies or star fields. In addition, standard optical filtering techniques may also be employed to enhance or otherwise alter the frequency response of the system and to develop, for example, specific color sensitivities.
Since the solid state TV camera is sensitive to the entire visible spectra and beyond, the video inspection system of the present invention may be applied to any task where the visible spectrum is involved. For example, secondary emissions of X-rays via fluoroscopy may be analyzed. Spectral analysis and colorimetry are also possible. Photographs of events can also be analyzed in a variety of ways. In short, the applications for the video inspection system of the present invention are limited only by the resolution of the sensor and the ability to develop appropriate image processing software.